Question

Find a specific example or report tying tooth morphology, tooth-marks, stomach contents, gastroliths, or coprolites to dietary assumptions we can safely make about a particular dinosaur clade.

Answer 1

ANSWER

The discussion will be carried out on two reports that are linked to the feeding behavior of the aquatic reptile Plesiosaur.

Coprolites or the fossilized fecal matter is not mentioned in any of the reports although evidences suggest that it doesn't provide much insights into the type of predation or feeding style of the organism. Intact coprolites and related evidences were not reported.

The Plesiosaur is well characterized with the presence of gastroliths and gastric content residues although the bone pieces of fish found did not show any traces of acid mediated processes that presents information regarding the kind of processes that helps in digestion. This information was put forth by Williston (1904, 1914) regarding presence of gastroliths in 6 different specimens observed. The pre-Cambrian time scale was associated with the feeding component of the reptile including body fishes (ancestral), sharks, cephalopods and this indicates their feeding habitat mainly restricted to the upper zones of the sea more specifically the pelagic zones and hence the body positioning in a manner in which the head region was uplifted. The homodont dentition in comparison with the recent mammals specified the feeding habit. As stated in a report, the homodont dentition might have led to the positioning of the preys as they did not use their teeth for chewing and mastication but directly swallowed the contents into the gastric cavity and this supported by the way in which the body of these organisms settled at the bottom and presence of anoxic conditions led to the depicted evaluation of the gastric contents after excavation of the caracass. Sato and Tanabe 1998, identified cephalopod beaks associated with the Plesiosaur ribs and abdominal skeleton. Wahl (1998) also depicted presence of cephalopod hook associated with the abdominal skeleton apart from traces of shark tooth and scales although presence of tooth was a rare phenomena and was suggestive only of the scavenging habit of the sharks.

So, this indicates a diversity in patterns of feeding with respect to scavenging seen under certain conditions. Presence of cephalopod and fish skeletons and bones associated with the gastroliths suggested a pelagic predatory nature. The gastroliths provided better evidence in terms of association with certain preferences although the role of gastroliths in the Plesiosaur is still not conclusive.

Shales from the Alzadasauros snowii species suggested presence of a region between the pelvic and the pectoral girdle specifying the right side portion of the reptile indicating fragmentation of the gastroliths and presence of gastric contents in a scattered manner but restricted to a small portion due to specialized process. Parrish and Gaultier came across the conclusion on the presence of anoxic conditions that supported the sustainance of the abdominal contents including the gastroliths and the skeleton associated contents. Round pebbles were associated with grinding activity after signifying no acidic content involved in digestion supported by the fact that these reptiles used the dentition and teeth arrangement to specify positioning of the preys into the abdominal region for swallowing. The teeth assembly and structure varied depending upon the zone of predation and the available preys. The teeth would be used for grinding as can be seen in very few fossil records indicating that certain shelled organisms were being crushed and this posed a question with respect to digestion carried out in terms of acidic contents. The report has stated a prominent relation between the birds and the Plesiosaur indicating the role of gastroliths to be similar in both the cases although some other concepts put forward also suggest the role of gastroliths acting as an aid to buoyancy which positioned the reptile in the upward direction and projecting their pelagic zone related predation (Carrol,1985). These are certain potential statements regarding the feeding nature of the Plesiosaur including an anatomical comparison for use of gastroliths. Certain investigators are reported which accordingly are important to be mentioned.

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